Atmos. Chem. Phys. Discuss., 13, 12797-12823, 2013
© Author(s) 2013. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Direct estimation of the rate constant of the reaction ClO + HO2 → HOCl + O2 from SMILES atmospheric observations
K. Kuribayashi1,2, H. Sagawa2, R. Lehmann3, T. O. Sato1,2, and Y. Kasai1,2
1Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503, Japan
2National Institute of Information and Communications Technology (NICT), Nukui-kita, Koganei, Tokyo, 184-8795, Japan
3Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany

Abstract. Diurnal variations of ClO, HO2, and HOCl were simultaneously observed by the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) between 12 October 2009 and 21 April 2010. These were the first global observations of the diurnal variation of HOCl in the upper atmosphere. A major reaction to produce HOCl is ClO + HO2 → HOCl + O2 (R1) in extra polar region. A model study suggested that in the mesosphere during night this is the only reaction influencing the amount of HOCl and ClO. The evaluation of the pure reaction period, where only reaction (R1) occurred in Cly chemical system, was performed by the consistency between two reaction rates, HOCl production and ClO loss, from SMILES observation data. It turned out that the SMILES data at the pressure level of 0.28 hPa (about 58 km) during night (between local time 18:30 and 04:00) in the autumn mid-latitude region (20–40° February–April 2010) were suitable for the estimation of k1. The rate constant was obtained to be k1(245 K) = 7.73 ± 0.26 (1σ) [× 10–12 cm3/molecule s] from SMILES atmospheric observations. This result was consistent with that from both the laboratory experiment and the ab initio calculations for similar low-pressure conditions. The 1σ precision of k1 obtained was 2–10 times better than those of previous laboratory measurements.

Citation: Kuribayashi, K., Sagawa, H., Lehmann, R., Sato, T. O., and Kasai, Y.: Direct estimation of the rate constant of the reaction ClO + HO2 → HOCl + O2 from SMILES atmospheric observations, Atmos. Chem. Phys. Discuss., 13, 12797-12823, doi:10.5194/acpd-13-12797-2013, 2013.
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